Call forwarding's USSD parser can't skip null string.

Call forwarding's USSD parser can't handle 120*1**20*1*0#.
Parser can't handle null string.

BUG: 119806564
Test: Manual test, fake the response msg,and check call forwarding info.
Change-Id: I14757b6f2fe13bcc243a135460825aa282f8aaf1
1 file changed